480 



TELEOSTEI 



[CH. 



a large dentary bone bearing teeth, the hinder part of which is 

 forked and ensheaths the articular bone, a cartilage bone already 

 described. Beneath the articular lies an angular bone. Behind 

 the lip bones a circum orbital chain of membrane bones extends 

 round the lower part of the eye. The first of these is larger than 

 the rest and is usually termed the lachrymal. Behind the circum- 

 orbital chain we come to the membrane bones which stiffen the 



12 





FIG. 236. Lateral view of the skull of a Salmon, Salino salar. After Parker. 

 Cartilage is dotted. 



1. Supra-occipital. 2. Epi-otic. 3. Pterotic. 4. Sphenotic. 5. Frontal. 

 6. Median ethmoid. 7. Parietal. 8. Nasal. 9. Lachrymal. 

 10. Suborbital. 11. Supra-orbital. 12. Cartilaginous sclerotic. 



13. Ossification in sclerotic. 14. Entopterygoid. 15. Metapterygoid. 

 16. Palatine. 17. Jugal. 18. Quadrate. 19. Maxilla. 20. Pre- 

 maxilla. 21. Articular. 22. Angular. 23. Dentary. 24. Hyoman- 

 dibular. 25. Symplectic. 26. Epihyal. 27. Ceratohyal. 



28. Hypohyal. 29. Glossohyal. 30. Opercular. 31. Subopercular. 

 32. Infra-opercular. 33. Pre-opercular. 34. Supratemporal. 



35. Branchiostegal rays. 36. Basibranchiostegal. 



operculum, that is the fold of skin which, as in Holocephali, arises 

 from the second visceral or hyoid arch and covers the gill-slits. 

 The most anterior of these bones is the long curved pre- oper- 

 culum lying just behind the symplectic; behind this is the 

 opercular bone. Beneath it is the suboperculum, and beneath 

 this again the interoperculum. The lower part of the opercular 

 flap remains comparatively flexible and is stiffened by a series of 



